Existing printhead circuits such as hot switch or cold switch driver ASICs for driving actuating elements have limitations in terms of their cost and power dissipation. So there is a question of how to provide electrical drive signals for an actuating element such as those having a piezoelectric actuator at the lowest circuit area (to reduce the cost) and with the lowest power dissipation while still meeting minimum drive requirements. Multiple drive methods for printhead actuating elements have been proposed and there are multiple different types in use today. Some are briefly discussed now.
Hot Switch: This is the class of driving methods that keep the demux function and the power dissipation (CV^2) in the same driver IC. This was the original drive method, before cold switch became popular.
Rectangular Hot Switch: This describes hot switch systems that have no flexible control over rise and fall time and only two voltages (0V and 30V for example). In some cases waveform delivery is uniform to all the actuating elements. The waveform has some level of programmability.
DAC Hot Switch describes a class of drive options that has a logic driving an arbitrary digital value stream to a DAC per nozzle, and outputs a high voltage drive power waveform scaled from this digital stream. In terms of driving flexibility, this option has the most capability. It is limited only by the number of digital gates and the complexity that system designers can use and/or tolerate.
Cold Switch Demux: This describes an arrangement in which all actuating elements are fed the same drive signal through a pass gate type demultiplexer. The drive signal can be gated at sub-pixel speeds.
It is also known to provide some factory calibration of differences between individual actuating elements and to provide compensation by “trimming” the drive signal applied to the different actuating elements. Such “trimming” may be effected by adjusting one or more of the drive waveform characteristics, for example voltage and/or slew rate. Patent application US20130321507 shows compensating for actuating element variations and changes by altering rise times of drive pulses for individual actuating elements which governs a rate of ejection of a droplet, and thus alters the appearance of a printed dot. The ejection rate is altered by changing an amount of series resistance or an internal resistance of a drive circuit according to a current sensing signal which indicates changes in actuating element capacitance from temperature or ageing effects.